1. Field of the Invention
This invention related to an improved structure for a gas turbine powered aircraft and to powerplants for use therein. In particular, but not exclusively, the invention relates to aircraft having a low bypass gas turbine engine mounted in the fuselage. However, the invention also extends to aircraft having wing-mounted and nacelle-mounted powerplants.
2. Discussion of Prior Art
In a conventional aircraft, the powerplant does not form part of the airframe of the aircraft. It is deliberately isolated from the main loads to which the aircraft is subject and which need to be transmitted and dissipated through the airframe structure. Such loadings include the loadings due to the wings, the fin, the taileron, the arrester hook etc. In conventional designs the airframe structure is designed to withstand these loads without transmitting them to the powerplant. The main loads to which the airframe is subjected are referred to hereinafter as the "airframe loads". Also, the term "airframe" is used in conventional manner to mean the load-bearing structure of the aircraft.
In a conventional design of aircraft with fuselage mounted powerplants, the airframe is designed to provide a bay into which the engine fits and the engine is typically attached to the airframe by a statically determinate mounting, i.e. a mounting which provides only one reaction force for each degree of freedom present within the system. This installation prevents airframe deflections from introducing loads into the powerplant, whilst allowing both axial and radial expansion of the engine due to thermal stressing during running.
Modern fighter aircraft are built according to his principle. The consequence of this is that, in the vicinity of the powerplant, most aircraft comprise a semi-monocoque construction consisting of an outer aircraft skin spaced from an inner aircraft skin by stringers or longerons to make up an airframe structure defining an engine bay. Within this engine bay is located the powerplant using a statically determinate mounting. Although this isolates the powerplant from the airframe loads, it is wasteful of space.